1. Field of the Invention
The present invention relates to a developing apparatus using a developer cartridge to exchange an old developer for anew one.
2. Description of the Related Art
In an image forming apparatus of a so-called electrophotographic type such as a copying machine, a facsimile, a printer, etc., an electrostatic latent image is formed in a latent image carrier. A developing apparatus of a dry type is widely used in such an image forming apparatus. In the developing apparatus using a developer composed of two components such as toner and carrier, the developer is deteriorated with the passage of time so that the quality of an image is reduced. Accordingly, it is necessary to exchange the old developer for a new one. When a developer cartridge is used in this exchange, an exchanging operation is simplified and an operator's hand, etc. do not become dirty with the developer.
In general, an empty developer cartridge is prepared in advance and an used developer is collected within the empty developer cartridge. Thereafter, a new unused developer is supplied into the developing apparatus from another developer cartridge. Accordingly, it is necessary to use two developer cartridges in the exchange of the developers so that the exchanging operation is very complicated.
As mentioned above, in the general developing apparatus, the exchanging operation is complicated and a user cannot exchange the old developer for a new one.
Therefore, the image forming apparatus has a first developer storage room for storing a new unused developer and a second developer storage room for storing an old used developer within one developer cartridge. After the old developer is collected within the second developer storage room, the new developer is supplied into the developing apparatus from the first developer storage room. In this case, it is sufficient to use only one developer cartridge so that the treatment of the developing apparatus is simplified.
When the new developer within the first developer storage room has been supplied onto a body side of the developing apparatus once in the exchange of the developers, developer characteristics such as fluidity are unbalanced since fluidity characteristics of the new unused developer are different from those of the used developer. Accordingly, the developer is deteriorated so that an image has an irregular density in a certain case.
Further, when the exchanging operation of the developers is performed during a copying operation in the image forming apparatus having the above developing apparatus, the copying operation must be interrupted once, thereby wasting time.
After the used developer is collected within the second developer storage room, the new developer is supplied into the body of the developing apparatus from the first developer storage room. A user must await the completion of the collecting and supplying operations of the developers so that wasting time is increased.
The developer within the first developer storage room is controlled with respect to toner density when this developer is forwarded from a factory. Accordingly, the developer has the same volume per unit weight. However, the toner density of the developer discharged from the body of the developing apparatus and collected within the second developer storage room is not necessarily constant.
This is because the density of the developer within the body of the developing apparatus is constantly controlled to perform a developing operation, but is not necessarily an initial density.
Accordingly, when the density of the developer is increased, a bulk density of the developer is increased so that the developer cannot be sufficiently collected within the second developer storage room having the same size as the first developer storage room.